It sounds as though we'd be able to do it in a non-D&D RAW way in BG3 if we didn't up all relevant stats to 13 to meet multi-classing prerequisites, but if we honour that in our build I'd understood it was actually permitted by the D&D rules as per this vid, which is presumably the inspiration for the achievement ...
"You may call it 'nonsense' if you like, but I've heard nonsense, compared with which that would be as sensible as a dictionary!"
